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  1. #21

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    Thank you Bill for your input. I can see now how I have been making more something out of nothing for the most part. I suppose though it would serve me well to wind off a roll from my bulk loader and do a little bit of gray card testing. I've been in photography since Methuselah finally kicked the bucket, but only here in the past couple years I've decided to set myself a pretty strict accuracy standard. !/4 stop would be nice, but 1/3 stop is a reasonable standard I hope you'd agree. Anything more just means more test stripping and foolishness in the darkroom.

  2. #22

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    Quote Originally Posted by Bill Burk View Post
    Hi Tom1956,

    The vendor's chart you found seems to illustrate three different products they offer, which seem to be designed to peak at different colors.

    The reference I found in Todd-Zakia Sensitometry gives a single CdS curve, probably an average of cells available at the time, that is a little less abrupt...

    Hi, I don't know if Todd and Zakia told what the (RCA) S-3 and S-11 are, but the designations sound like they may be photomultiplier tubes. If so, they would have been more at home in an densitometer from that time period than in a hand-held exposure meter.

    All of those sensors could have had their response manipulated just about anywhere with filters, so one should keep in mind that an actual exposure meter might not respond the same as the sensor data indicates.

  3. #23

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    Quote Originally Posted by Tom1956 View Post
    Perhaps put another way, black and white film tungsten ratings, or metering in other lighting conditions than daylight. I believe it is universally accepted that exposure meter sensitivity is planned to be in the 5600K neighborhood of color temperature. But what about metering in other lighting?
    I don't know what current ISO standards call for, but going back to 1970s ANSI standards, the reference standard was 4700 K. (see the following)

    From ANSI PH3.49 - 1971, Appendix B:

    The primary standard for color temperature of a 4700 K radiation consists of a tungsten lamp operated at 2854 K in combination of the Davis and Gibson filter. This source not only matches closely the spectral-energy distribution of a blackbody at 4700 K, but is also reproducable from specifications.
    All they had to say about spectral response requirements for the meter was that it had to be "continuous in the range between 350 nm and 700 nm." But the test seemed less complete, only requiring that the light detector match readings (at fixed luminances) at 2854 K vs 4700 K.

  4. #24
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    Quote Originally Posted by Tom1956 View Post
    Thank you Bill for your input. I can see now how I have been making more something out of nothing for the most part. I suppose though it would serve me well to wind off a roll from my bulk loader and do a little bit of gray card testing. I've been in photography since Methuselah finally kicked the bucket, but only here in the past couple years I've decided to set myself a pretty strict accuracy standard. !/4 stop would be nice, but 1/3 stop is a reasonable standard I hope you'd agree. Anything more just means more test stripping and foolishness in the darkroom.
    I agree 1/3 stop is a good goal. I personally adopted 2/3 stop for my goal. Just seems to me that a mistake in any assumption would lead to 1/3 stop "error" - so the best I hope for is that a couple of 1/3 stop errors cancel each other out... leaving me within 2/3 stop of what the exposure should be (if I make four errors).

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